watchOS 4.2 (build 15S102) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2017-12-05T18:00:55Z. The update package is 221.65 MB. This is a delta (partial) update that requires 4.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: bd033d8385eb6977dd216d8ab9866a9a17d75619.zip.